This invention relates generally to metal separators. More specifically, but not by way of limitation, the invention is directed to an apparatus for separating non-ferrous metal material from ferrous metals, rocks, glass, wood, rubber, dirt and other such debris by means of an eddy current.
1. Background Art
In this present era of recycling and limited land-fill space, the necessity to reclaim reusable materials from debris and waste has become an utmost concern of our society. The reclamation of metal materials is additionally important due to the increasing scarcity of these natural resources and the cost-effectiveness of recycling versus mining and purification of metals. To recover metals from debris and waste, the recycling industry has developed numerous metal separating devices.
These separation devices include both magnetic separators and eddy current separators. Magnetic separators allow ferrous metal pieces to be easily removed by suitable magnets which sort the ferrous metals from the debris using attractive magnetic forces to pull the ferrous metals from the balance of the debris. Alternative methods are required in removing non-ferrous metals since they do not contain the magnetic properties of ferrous metals.
Magnetic separation typically works by attracting items to be separated from a group or mixture. Eddy current separators, on the other hand, repulsively act upon conductive materials or particles which are not magnetic in nature, such as aluminum, copper and brass. Eddy current separation functions by inducing or sweeping a high density, rapidly changing, magnetic flux through the mixture so that eddy currents are created in any appropriately conductive non-ferrous particles. The eddy current subjects these conductive particles to a resultant repulsive force away from the eddy current source. The magnitude of this repulsive force is defined by electrical resistivity, size and shape of the conductive particle, the strength of the magnetic flux field, and the frequency of pole changes in the magnetic flux field. If sufficiently strong, the repulsive force causes the non-ferrous particles to be thrust away from the magnetic flux field, thereby separating these particles from non-electrically conductive material in the mixture or debris. Thus, while similar structural elements may be employed in separators of both the magnetic and eddy current types, their modes of operation, the relative orientations of the structural elements, and the resulting effects caused by the two apparatus are substantially different.
A review of known patents discloses several inventions embodying this type of eddy current separation device. U.S. Pat. No. 5,080,234 to Benson utilizes a pair of cylinders, one positioned above the other, that are rotated synchronously in opposite directions from each other and are coordinated so that poles of opposite polarity face each other across an air gap. An eddy current is induced in electrically conductive particles as the particles are conveyed across the gap. The current repulses the particles thereby allowing their separate collection apart from the free-falling non-conductive material in the debris.
In another separating apparatus disclosed in U.S. Pat. No. 5,092,986 to Feistier et al., a rotating drum consisting of magnets is eccentrically placed adjacent to a belt drum. Debris is conveyed across the belt drum by means of a conveyor belt. The magnetic drum produces a magnetic flux field from which eddy currents are created in electrically conductive particles of the debris as the particles are conveyed along the belt over the belt drum. The conductive particles are projected further off of the belt than other material due to the repulsive magnetic force generated by the drum. In this manner, the electrically conductive particles are separated from the remaining debris. A scraper is employed to remove iron particles attracted to the magnets thereby aiding in preventing damage to the belt drum.
In today""s recycling industry, predominately metal products such as automobiles, refrigerators, washing machines, etc., are shredded into small pieces. These small pieces are then run through trommel screens that sift out dirt, glass and other sufficiently fine particles from the shredded product. The larger pieces that remain within the drum of the trommel are collectively referred to as residue; a material that often includes dirt, rocks, glass, wood, rubber, and various metal pieces such as aluminum, copper and brass.
The residue is classified and purchased on a relative percentage basis of metal to total material; for example, xe2x80x9c30% residuexe2x80x9d indicates that the combination is comprised of thirty percent metals, while the remaining matter is a mixture of non-metals that may include dirt, trash, rubber, and other matter. Typically, forty-five thousand pound truckloads of residue are purchased at a time by a recycling or processing plant. In the instance of a thirty percent residue load, roughly thirty thousand and five hundred pounds of unusable material is shipped to the plant and must ultimately be discarded or otherwise processed. Obviously, the recycling plant desires the percentage of residue shipped to be as high as possible so that resources are not wasted on the transport of unusable material. In at least one past instance, residue was purified by water and/or heavy media plants which proved to be costly. Out of this dilemma the eddy current separating industry evolved.
Most present-day eddy current machines are typically comprised of a rotor within a nonmetallic drum pulley design. In some instances, the magnetic rotors have a rotational axis off the centerline of the drum pulley shaft for the conveyor belt and are referred to as eccentric designs. Others are concentrically oriented and the rotors rotate about a common axis with the pulleys about which the conveyor belts wrap. The inner rotor contains the magnet, or magnets and is enclosed within the larger, outer belt drum. The outer drum is typically comprised of a fiberglass or a ceramic coated material. Iron attracted to the magnets tends to accumulate on the outer drum. The presence of the iron creates resistance resulting in heat, thereby burning through the fiberglass belt drum and sometimes damaging or destroying the magnets, and possibly the rotor itself. This damage is due to the tight tolerances at which the two rotating components are run with respect to one another. To potentiate the combined performance of the two components, the inner magnetic rotor is run as closely as possible to the outer belt pulley drum so that the induced magnetic field is as close as possible to the material being separated.
In view of known complications associated with current separator designs, the magnetic separator of the present invention has been designed to provide a cost-effective means of overcoming damage to the magnetic rotor during the separation process of the fragmented material by eliminating required operation of the rotor within the belt pulley drum. The present invention provides a means whereby the magnetic rotor is separately included, as opposed to an eccentric or concentric arrangement of two rotating components. It also provides a means by which preventive maintenance, parts replacement and equipment repairs are greatly simplified due to the separator""s design. These features also result in cost-savings and reduced downtime.
2. Disclosure of the Invention
The present invention in its several disclosed embodiments alleviates the drawbacks described above with respect to the separation of non-ferrous metal material from ferrous metals, rocks, glass, wood, rubber, dirt and other such debris by means of any eddy current which incorporates several beneficial features. An eddy current separator apparatus is disclosed whereby electrically conductive metals are separated from other materials such as glass, rubber, wood, rocks and dirt in a novel and unique manner. The present invention separates non-ferrous metals from the debris by a shredding process through the utilization of a single magnetic rotor. The effect of the magnetic rotor is to upwardly lift or boost the non-ferrous metals as they travel upon a continuous belt. The lifting boost of the rotor, together with the lateral inertia induced by the moving belt applies a resultant force upon the non-ferrous metals that xe2x80x9cthrowsxe2x80x9d the affected metals further beyond the end of the belt than the remainder of the debris.
The magnetic rotor takes the form of a rotating shaft or drum that contains elongate magnets having north and south poles radially oriented upon a rotor shaft. Each magnet is positioned so that a longitudinal centerline of the magnet""s body is oriented parallel to an axis about which the magnet is revolved, but substantially perpendicular to its north and south polarity axis.
The rotational axis of the magnetic rotor is arranged substantially perpendicular to the travel path of the conveyor belt. The drum normally rotates just inside of a return end of the conveyor belt about which the direction of travel for the belt changes. In this way the exterior of the rotor""s outer skin can be positioned just beneath the interior surface of the belt.
When appropriately rotated, the magnetic rotor induces a repulsive force in the non-ferrous material. The rotor is oriented so that the generated force is substantially aligned with the direction of travel of the top surface of the belt. The repulsive force is directed generally away from the rotor and across the conveyor belt in a manner that serves to boost the trajectory of the affected material pieces so that they are projected off of the end of the conveyor belt as it wraps back in the opposite direction about a nose idler or return pulley. The unaffected particles are not boosted, but are merely projected off of the end of the belt by the inertial force established by their travel upon the top moving surface of the conveyor belt. Separation of the two differently affected groups (non-ferrous versus other material) is most advantageously planned based on the different projection distances of the different materials from the end of the belt.
The separator machine of the present invention comprises a metal frame upon which other components are attached. A seamless, continuous conveyor belt is positioned to cover an upper surface or belt pan at the top of the frame. A first motor attached rearwardly to the frame drives the conveyor belt in a continuously wrapping loop at the top of the frame. This first motor drives the belt at speeds that are preferably variable between one hundred feet per minute and seven hundred feet per minute. A second motor is attached forwardly for independently driving the magnetic rotor. Additional smaller belt drums or idler pulleys are positioned along the belt""s path in order to give stability and direction to the belt""s operation.
In a preferred embodiment, the belt is seamless and optionally carries one or more wipers upon an exterior surface, each wiper being transversely oriented to the direction of the belt""s travel. The wipers are included to sweep debris from the belt that may ride thereon by rolling at a similar speed, but in an opposite direction to the motion of the belt""s upper surface. The wiper also sweeps ferrous material that is attractively retained in the magnetic field above the rotor.
A belt pan is provided having a top surface that facilitates the sliding of the conveyor belt across the pan""s top surface. In a preferred embodiment, at least the top surface of the belt pan is constructed from, or coated with an ultra-high molecular weight material that is slippery when engaged by a dry surface, such as the interior surface of the conveyor belt. The pan also lends stability and support to the belt""s operation. This may be appreciated in view of the fact that heavy pieces of debris are continuously being dropped thereupon and quickly accelerated to a velocity equal to the travel speed of the belt itself.
The magnetic rotor is positioned adjacent to the belt""s inner surface with a clearance space there between which in some cases may measure zero. One or more reduced friction tiles are utilized to provide an inclined sliding surface upon which the substantially horizontal travel of a top surface of the conveyor belt is broken and redirected downwardly for return in a looping fashion around the nose idler and beneath the top belt surface. The magnetic rotor is oriented so that its boosting force acts at the top of the downward incline thereby enhancing the distance of projection of affected items off of the end of the conveyor belt. The separating capabilities are enhanced by the other debris"" natural tendency to fall downwardly at the incline under gravitational effects when no longer supported upon the traveling belt.
The described configuration heightens the separating capability of the invention by having a substantial spacial spread between the distances at which the two groups of materials are being projected from the end of the conveyor belt. By appropriately orienting separating means, such as a dividing partition or partitions with respect to the end of the belt between the two landing areas for the different materials, material separation is accomplishable. In a preferred embodiment, the material that is unaffected by the eddy current drops onto a removing conveyor belt located relatively close to the separator""s frame, while the affected non-ferrous material is xe2x80x9cpitchedxe2x80x9d to a receiving receptacle located further from the separator, normally on a far side of the removing conveyor belt away from the belt""s point of discharge.
Hubs covering the ends of the magnetic rotor are positioned at a distance beyond longitudinally distal ends of the magnets. This spacing distance results in only a nominal magnetic field being induced or created at the ends of the rotor, thereby greatly reducing the likelihood that ferrous particles will be attracted to, and pulled around and under the conveyor belt for adherence to the magnetic rotor. Equally important, the potentially harmful ferrous particles are much less likely to be pulled into the interior of the magnetic rotor where severe damage can result because the hubs are sealingly engaged upon ends of what is preferably a metallic skin drum surrounding the rotor assembly. In this manner, a sealed interior compartment is established for housing the magnets.
Material guard rails are provided along both sides of the top portion of the belt to maintain material on the belt during operation. Threaded hand knobs secure the rails to the frame and are adapted so that the rails can be quickly removed and reinstalled for repairs and maintenance that require removal of the conveyor belt. A top portion of the guard rails diverge outwardly for better retention of traveling matter thereupon.
The supporting frame is of a cantilever design that permits easy access to all points about the conveyor belt. This is attributable to the fact that the table top portion of the separator about which the continuous belt wraps and rotates is exclusively supported at its back side and extends forward therefrom in a cantilever manner. In this configuration, there are no support members located beneath the front of the table that impede the removal or installation of a continuous belt about the table top. In this way, the belt acts in a sleeve-type manner about the supporting table top. This design allows a single operator to easily and quickly remove and install a belt.
The rear belt drive pulley is drum-styled and carried on rotatable spherical pillow block bearings positioned at each end of an axle-type shaft. Each bearing allows the longitudinal axis of the drum, which is coincident with the center axis of the axle shaft of the drum, to be pivoted within a limited 360 degree conical solid having an apex point located substantially at the center of the bearing. In light of this capability, the rear belt drum may be laterally pivoted in a substantially linear direction parallel to the direction of travel of the continuous belt. This forward and backward movement of the front end of the belt pulley opposite the rotatable spherical pillow block bearing is accomplished by the manipulation of an adjustment mechanism manually actuated by a handled lever. As the front end of the belt drum is moved inwardly and outwardly with respect to the separators frame, the race or track upon which the belt is supported constricts and expands. In the expanded configuration, an installed continuous belt fits tightly thereabout and is oriented for operation. In the constricted or contracted configuration, the belt is slackened and may easily be removed from or installed about the table top of the separator.
In at least one embodiment, the present invention takes the form of an eddy current separator apparatus for separating non-ferrous metals from other materials. The apparatus includes a support frame and a table cantileverly suspended from the frame. An expansion and contraction mechanism is incorporated and adapted to accept a continuous conveyor belt thereabout. The expansion and contraction mechanism is capable of being configured between an operating configuration and maintenance configuration. A continuous conveyor belt is constructed to be able to be looped about the expansion and contraction mechanism and the table such that the conveyor belt is drawn tight in the operating configuration and slackened in the maintenance configuration. In this manner, the continuous conveyor belt is easily removable from, and installable onto the table in the maintenance configuration. A magnetic rotor is positioned proximate a first side of the continuous conveyor belt and is adapted to generate an eddy current on an opposite second side of the continuous conveyor belt upon rotation for inducing an elevating force in non-ferrous metals for separation from other materials.
Accordingly, some of the objectives of this invention, among others are to provide, inter alia: an improved eddy current separator apparatus; an eddy current separator apparatus that is cost-effective to produce and operate; an eddy current separator apparatus that minimizes downtime for repair and maintenance; an eddy current separator apparatus that can be repaired quickly by one operator; and an eddy current separator apparatus comprised of a singular magnetic rotor located directly adjacent to the continuous conveyor belt upon which non-ferrous electrically conductive metals are transported.
Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.